FIG. 1 of the accompanying drawings is a schematic diagram used to explain a principle of an optical system of a reflecting confocal scanning microscope which is often referred to as "CSM".
As shown in FIG. 1, in a reflection type confocal scanning microscope 1, light L from a point source (laser light source) 2 is reflected on a half mirror 3 and focused on a target object 5 set at the focus position by an objective lens 4. Reflected light reflected by the target object 5 is traveled through the objective lens 4 one more time and passed through the half mirror 3, whereafter it is detected by a point detector 6. In order to construct a confocal system, a point detector is placed at the position of a virtual image of the point source 2. Alternatively, a pinhole 7 is disposed as shown in FIG. 1 such that all rays of light passed through the pinhole 7 are detected by a surface detector (photo detector 6). Then, the target object 5 is microscopically scanned in a three-dimensional fashion and an image processing is carried out, thereby an image of a three-dimensional optical microscope image being obtained. Since the reflection type confocal scanning microscope 1 has the confocal optical system as described above, there can be obtained an image having remarkable characteristics, such as high contrast, having no coherent noise or having ultra-high resolution.
However, the confocal scanning microscope 1 is large in scale. Moreover, the confocal scanning microscope 1 typically requires significant time for measuring an object and has to process information of a large amount at high speed. As a consequence, the confocal scanning microscope is not suitable for handy measuring and cannot measure a target object which changes rapidly.
On the other hand, in an optical recording and reproducing apparatus for recording and reproducing an optical disk, such as a compact disc (CD), a write once compact disc (CD-R) or magneto-optical disk, an information processing speed, i.e., a transfer rate at which information is read and written is limited. Furthermore, since an information recording density is of a two-dimensional one, an amount of information is limited.